A NEW APPROACH TO THE DESIGN OF SIGMA-2-SELECTIVE LIGANDS - SYNTHESISAND EVALUATION OF THYL]-N-METHYL-2(1-PYRROLIDINYL)ETHYLAMINE-RELATED POLYAMINES AT SIGMA-1 AND SIGMA-2 RECEPTOR SUBTYPES
Br. Decosta et al., A NEW APPROACH TO THE DESIGN OF SIGMA-2-SELECTIVE LIGANDS - SYNTHESISAND EVALUATION OF THYL]-N-METHYL-2(1-PYRROLIDINYL)ETHYLAMINE-RELATED POLYAMINES AT SIGMA-1 AND SIGMA-2 RECEPTOR SUBTYPES, Journal of medicinal chemistry, 37(2), 1994, pp. 314-321
A series of polyamines based on the high affinity sigma receptor ligan
d henyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamine (3) were develope
d and evaluated for their binding characteristics at sigma-1 and sigma
-2 receptor subtypes. The data indicated that a considerable degree of
structural variation is possible while still retaining nanomolar affi
nity at a receptors; As the structure of the polyamines was varied, th
eir binding at sigma-1 and sigma-2 subtypes showed quite different and
in some cases opposite trends, supporting the belief that these are p
harmacologically distinct entities. Polyamines containing two nitrogen
atoms showed optimal binding at both sigma-1 and sigma-2 receptor sub
types. Although additional nitrogen atoms resulted in decreased affini
ty at sigma-1 and sigma-2 subtypes, an increase in selectivity for sig
ma-2 subtypes was evident; the parent 3 showed greater selectivity for
sigma-1 subtypes. Internitrogen spacings had a large effect on bindin
g affinity and subtype selectivity. For example, the difference betwee
n -(3,4-dichlorobenzyl)-N,N'-dimethylethylenediamine (8) [K-i = 29.9 n
M at sigma-1 receptor and 18.3 nM at alpha-2 receptor] to ]-N'-(3,4-di
chlorobenzyl)-N/N'-dimethylethylenedi- amine (10) [K-i = 1.49 nM at si
gma-1 receptor and 12.1 nM at sigma-2 receptor] illustrates the import
ance of internitrogen spacing. Triamines 11 and 13 [K-i(sigma-2)/K-i(s
igma-1) = 0.19 and 0.10, respectively] containing the N-N-N-Ar spacing
s 3-3-2 and 4-4-2, proved to be the most sigma-2 subtype selective of
the 15 polyamines examined in this study. The N-N-N spacings appear to
be an important factor in their sigma-2 subtype selectivity. These co
mpounds will serve as templates in the design of still further sigma-2
subtype selective ligands. The pyrrolidine ring (present in most of t
he polyamines tested in this series) proved to be an important recogni
tion site for a receptor binding activity. Furthermore, alkyl substitu
tion also appears to be important since the stripped down polyamines N
-[2-(3,4-dichlorophenyl)ethyl]ethylenediamine (15) and N-1-[2-(3,4-dic
hlorophenyl)ethyl] diethylenetriamine (16) exhibited relatively low bi
nding affinity.